Aeroterrestrial Microalgae Growing in Biofilms on Facades—Response to Temperature and Water Stress

Abstract

The photosynthetic performance of a microalgal biofilm colonizing a building facade was investigated between February and July 2004, with an emphasis on changing water availability and air humidity. The fluorimetric measurements of the quantum efficiency (F (v)/F (m)) indicated diurnal activity patterns. At most sampling dates the algal biofilm photosynthesized particularly in the morning and substantially less in the afternoon. As long as liquid water was present, the microalgae exhibited at least some degree of photosynthesis. However, F (v)/F (m) values never exceeded 0.4, pointing to slight photoinhibition or damage of the cells. Dried cells without photosynthesis could recover within minutes after artificial moistening. Three microalgal strains were isolated from aeroterrestrial biofilms and established as unialgal cultures. Their photosynthesis and growth were characterized under different air humidities and temperatures. Photosynthesis and growth of strain ROS 55/3 (Stichococcus sp.) showed similar patterns with decreasing relative air humidity. Positive growth and optimum photosynthesis were recorded at 100% relative air humidity. At air humidities below 93%, both processes were strongly inhibited. All studied strains grew between 1 and 30 degrees Celsius with optimum rates at 20-23 degrees Celsius, indicating eurythermal features. The data indicate that liquid water or 100% air humidity are the prerequisite for optimum photosynthesis and growth of aeroterrestrial microalgae. However, when dried and consequently inactive, these microorganisms can recover quickly if water is suddenly available, e.g., after rain events. These physiological capabilities explain well the ecological success of aeroterrestrial microalgae in occupying many man-made substrata such as building facades and roof tiles in urban areas.

Electrochemical behavior of the 316L steel type in a marine culture of microalgae (Porphyridium purpureum) under the 12/12 h photoperiod and effect of different working electrode exposure conditions on the biofilm–metal interface

“…In our opinion, the position of the samples especially brings into play the diVerent forces of adhesion for the immersed samples at half, where there exists a gradient of moisture on the surface of the material between the immersed part and the air part. This case is similar to the one described by Haubner et al [11] when they studied aeroterrestrial microalgae growing in bioWlms on facades in the interface between hard substrata and the atmosphere. They concluded that this phenomenon was a response to temperature and water stress.…”

Community structure of corticolous microalgae within a single forest stand: evaluating the effects of bark surface pH and tree species

“…The other attributes of tree bark (besides pH) that may be responsible for the observed variation remain unknown. LüTTGe &BüdeL (2010) andhäuBNer et al (2006) found that varying tolerance to desiccation stress may be a key factor determining the survival ability of microalgal taxa in aerial biofilms. The tree species-dependent bark water-holding capacity (related to bark thickness, hardness, texture and stability) and stem flow (resulting from tree crown morphology) directly influence the intensity of desiccation stress and are important determinants of the distribution of various bark-dwelling organisms (valová & Bieleszová 2008;Büdel 2011;ellis 2012).…”

Effects of UV radiation on optimum quantum yield and sunscreen contents in members of the generaInterfilum, Klebsormidium, HormidiellaandEntransia(Klebsormidiophyceae, Streptophyta)

“…Terrestrial algae often develop thick cell walls (Karsten & Holzinger, 2014), in many cases with mucilage layers or with incorporated macromolecules such as sporopollenins or sporopollenin-like substances (algenans) that might absorb the UVR (VanWinkle-Swift & Rickoll, 1997;Pescheck et al, 2010). In addition, under natural conditions, terrestrial green algae are most often incorporated into biofilms, while Klebsormidium species can form multi-layered structures on top of or interwoven with the upper millimetres of soil particles (Häubner et al, 2006). Both microstructures most probably contribute to a high degree of self-shading and hence photoprotection of individual cells inside such a population.…”